The present invention relates to a method of friction filler welding for joining objects (workpieces) to be welded, such as rails or reinforcement, easily and securely.
Although joining methods such as electric arc welding or gas-pressure welding are conventionally adopted when rails etc. are connected to each other by the end faces for elongation, the above conventional joining methods are accompanied by inevitable occurrence of a weld defect or an embrittled structure, since any welding method once melts joining portions and then joins them.
To solve the drawback in the above joining methods, a rotational friction welding has been developed in these days. See, for example, xe2x80x9cWelding and Joining Manualxe2x80x9d (edited by Japan Welding Society, publisher: Maruzen Inc., pp. 480-489) as a reference.
However, such rotational friction welding generates a required thermal energy for welding by rotating at least one of workpieces to be joined; therefore, problems remain in that it is technically difficult and impractical to rotate the workpieces themselves, especially when the workpieces are bulky or long, or have variant cross sections.
The object of the present invention is to propose a novel method of friction filler welding which is capable of joining easily and securely without having any limitation on the size and the configuration of the workpieces, or being accompanied by the weld defect.
The present invention is related to a method of joining at least two workpieces at their end faces by friction filling welding, said method comprising the steps of:
arranging an intermediate member as a filler between opposed end faces of the workpieces,
pressing said workpieces against each other via the intermediate member to produce friction pressure therebetween while rotating or vibrating the intermediate member at a high speed, and
upsetting each workpiece to the intermediate member on bringing the rotation or the vibration of the intermediate member to a halt.
In the present invention, the pushing velocity of the workpiece represents the velocity in which the workpiece is pushed against an intermediate member by giving an external force upon the workpiece. Herein, the approach velocities of the workpiece during generating the friction pressure and upsetting the workpieces are preferably 0.01-5 mm/s. Also, the number of revolutions of the intermediate member is preferably 100-10,000 rpm, or the frequency of vibrations for the intermediate member is preferably 10-1,000 rpm.
When the workpieces are upset, it is required to secure the soundness of the joined portion and to deform the intermediate member sufficiently to enforce the joint. Therefore, the pressure of upsetting the workpieces is preferably equal to or greater than the friction pressure generated in the high-speed rotation or vibration of the intermediate member.
Especially, the period of time to press the workpieces against the intermediate member which is rotating or vibrating at a high speed is preferably 1-1,000 seconds and the period of time of upsetting the workpieces is preferably 1-100 seconds.
Additional aspects and advantages of this invention will be apparent from the following detailed description of preferred embodiments thereof, which proceeds with reference to the accompanying drawings.